Separation Process Principles- 2n - Seader & Henley - Solutions Manual

4of compared to assumed value of 300of stage 2

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Unformatted text preview: liquid at column pressure of 250 psia. Column has a partial condenser, partial reboiler, and 15 equilibrium stages in the column with feed entering the middle stage. Distillate rate = 23.0 lbmol/h and reflux rate = 150.0 lbmol/h. Soave-Redlich-Kwong equation of state for K-values and enthalpies. Find: Product compositions. Stage temperatures, vapor and liquid flow rates, and compositions. Reboiler and condenser duties. Analysis: The calculations were made with the TOWER model (Inside-out method) of the Chemcad program, with the following specifications: Partial condenser Top pressure = 250 psia No condenser or stage pressure drop. Therefore, bottom pressure also = 250 psia Number of stages = 17 (includes partial condenser and partial reboiler) Feed stage = 9 from the top Sidestream from stage 13 from the top, as a vapor at a flow rate of 37 lbmol/h At the top, reflux rate = 150 lbmol/h At the bottom, bottoms rate = B = F - D - S = 100 - 23 - 37 = 40 lbmol/h Estimated distillate rate = 23 lbmol/h (actual rate) Estimated reflux rate = 150 lbmol/h (actual rate) Estimated temperature of stage 1 = 120oF Estimated temperature of bottom stage = 300oF Estimated temperature of stage 2 = 140oF Although the feed was given as a bubble-point liquid at 250 psia and 213.9oF, the SRK equation of state gave a bubble-point temperature of 210.7oF, which was the value used. Based on the feed composition below, the distillate rate of 23 lbmol/h corresponded to a desired split between propane and n-butane. The calculations converged rapidly in 3 outer-loop iterations with results given below and on the following pages. The vapor side stream contains 69.5 mol% nC4. Condenser duty = 914,000 Btu/h Reboiler duty = 1,440,000 Btu/h Top temperature = 124.4oF compared to assumed value of 120oF Bottom temperature = 290.5oF compared to assumed value of 300oF Stage 2 temperature = 140.9oF compared to assumed value of 140oF Analysis: (continued) Exercise 10.22 (continued) Analysis: (continued) Exercise 10.22 (continued) Exercise 10.23 Subject: Distillation with an intercooler and an interheater Given: Conditions given in Exercise 10.20 except that an intercooler with a duty of 200,000 Btu/h is placed on the fourth stage from the top (Stage 5 counting the partial condenser), and an interheater with a duty of 300,000 Btu/h is placed on the fourth stage from the bottom (stage 13 from the top counting the partial condenser). Therefore, the remaining specifications are still a feed of composition below as a bubble-point liquid at column pressure of 250 psia. Column has a partial condenser, partial reboiler, and 15 equilibrium stages in the column with feed entering the middle stage. Distillate rate = 23.0 lbmol/h and reflux rate = 150.0 lbmol/h. Soave-RedlichKwong equation of state for K-values and enthalpies. Find: Product compositions. Stage temperatures, vapor and liquid flow rates, and compositions. Reboiler and condenser duties. Analysis: The calculations were made with the TOWER model (Inside-out method) of the Chemcad program, with the following specifications, where TOWER treats intercooler...
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